1. Field of the Invention
The present invention relates to a valve that responds to the presence of a particular substance in fluid flowing through the valve, such as the presence of hydrocarbon in a flow of water.
2. Description of the Related Art
In the petroleum industry, it is often possible for hydrocarbon to leak into a flow of water that is discharged into the environment. For example, a hydrocarbon storage tank (such as is found in a xe2x80x9ctank farmxe2x80x9d) often has an internal drain pipe to allow drainage of water from a fixed or floating roof of the tank. It is possible for an internal drain pipe to leak, causing stored hydrocarbon to drain from the tank. To prevent the contents of the tank from being drained to the atmosphere or ground, the discharge end of the drain pipe should be fitted with a hydrocarbon sensing automatic shutoff drain valve.
Hydrocarbon sensing automatic shutoff drain valves are described in Fraylick et al. U.S. Pat. No. 3,491,911 issued Jan. 27, 1970; Thiltgen U.S. Pat. No. 5,036,875 issued Aug. 6, 1991; and Partridge U.S. Pat. No. 5,960,811 issued Oct. 5, 1999. These automatic shutoff drain valves employ a hydrocarbon soluble triggering element disposed in the discharge flow, and a spring that closes the valve upon dissolution of the triggering element. The valves are intended to close in response to a relatively small trickle of water containing hydrocarbon. However, the flow through the open valve should not be unduly restricted or else clogging may occur from debris which is often present in drainage from tank roofs. Yet it is most desirable that the valve will close in a reliable fashion as soon as possible after hydrocarbon begins to flow through the valve.
Conventional hydrocarbon sensing valves use a polystyrene sensor element that dissolves quickly in gasoline but dissolves rather slowly in medium to heavy hydrocarbon such as diesel fuel, fuel oil, or crude oil. Consequently, the conventional hydrocarbon sensing valves have rather poor closure time in the presence of medium to heavy hydrocarbon. It is desired to achieve a closure time in the presence of medium to heavy hydrocarbon that is comparable to the closure time of conventional hydrocarbon sensing valves in the presence of gasoline. Therefore, the present invention is directed to reducing the time for a sensing valve to close when the sensor element is slowly dissolving or disintegrating due to the presence of a fluid flowing through the valve.
In accordance with one aspect of the invention, there is provided a method of shutting off a flow of fluid when a substance is present in the fluid. A tensile load is applied to a sensor element that will carry the tensile load in the absence of the substance and will fail to carry the tensile load in the presence of the substance. The sensor element is disposed in the flow of fluid, and a flow control member is actuated to shut off the flow of fluid when the sensor element fails to carry the tensile load.
In accordance with another aspect of the invention, there is provided a sensing valve for shutting off a flow of fluid when a substance is present in the fluid. The sensing valve includes a housing having an inlet port and an outlet port; a flow control member, and a sensor element. The flow control member is disposed in the housing for permitting the flow of fluid from the inlet port to the outlet port when the flow control member is in an open position, and shutting off the flow of fluid from the inlet port to the outlet port when the flow control member is in a closed position. The sensor element is responsive to the presence of the substance in the fluid, and the sensor element is coupled to the flow control member and the housing for causing the flow control member to move from the open position to the closed position when the substance is present in the fluid. In addition, the sensor element is coupled to the flow control member and the housing for applying a tensile load to the sensor element and causing the flow control member to move from the open position to the closed position when the sensor element fails to carry the tensile load in response to the presence of the substance in the fluid.
In accordance with yet another aspect, the invention provides a sensing valve for shutting off a flow of fluid when a substance is present in the fluid. The sensing valve includes a housing, a flow control member, a sensor element, and a channel member. The housing has a generally horizontal pipe section providing an inlet port, and the housing has a generally vertical cylindrical section providing an outlet port at a lower region of the generally vertical cylindrical section. The flow control member is disposed in the generally vertical cylindrical section of the housing for permitting the flow of fluid from the inlet port to the outlet port when the flow control member is in an open position, and shutting off the flow of fluid from the inlet port to the outlet port when the flow control member is in a closed position. The sensor element is responsive to the presence of the substance in the fluid and coupled between the flow control member and the housing for causing the flow control member to move from the open position to the closed position when the substance is present in the fluid. The sensor element is coupled between the flow control member and the housing for applying a tensile load to the sensor element and causing the flow control member to move from the open position to the closed position when the sensor element fails to carry the tensile load in response to the presence of the substance in the fluid. In addition, the sensor element is seated in a cavity in the top of the flow control member, and the sensing valve has a channel member for directing the flow of fluid from the inlet port to the cavity in the top of the flow control member. The sensor element is pinned to the channel member by a first pin, and the sensor element is pinned to the flow control member by a second pin.
In accordance with still another aspect, the invention provides a sensing valve for shutting off a flow of fluid when a substance is present in the fluid. The sensing valve includes a housing, a flow control member, a sensor element, and a channel member. The housing has a generally horizontal pipe section providing an inlet port, and the housing has a generally vertical cylindrical section providing an outlet port at a lower region of the generally vertical cylindrical section. The flow control member is disposed in the housing for permitting the flow of fluid from the inlet port to the outlet port when the flow control member is in an open position, and shutting off the flow of fluid from the inlet port to the outlet port when the flow control member is in a closed position. The sensor element is responsive to the presence of the substance in the fluid and coupled to the flow control member and the housing for causing the flow control member to move from the open position to the closed position when the substance is present in the fluid. The channel member is seated in the cylindrical section of the housing for directing the flow of fluid from the inlet port to the sensor element. In addition, the housing includes a removable cover, the flow control member and the sensor element are mounted to the channel member, and an assembly of the channel member, the flow control member, and the sensor element is removable from the housing when the cover is removed to open the housing.